Not so cheap 2.0 mods.

So I've been doing a LOT of reading lately, and frankly I'm too tired to do another search.

I have a mkiv AVH 2.0 golf. So far I've cut the air box (looking at a P-Flo or something next maybe), put in a 'stage 3' ported intake manifold, installed a TT 260 cam, a Unitronic tune, and a manifold back Magnaflow exhaust (2.25" mandrel bent). I've also done a lightweight crank pulley, a stage 1 clutch with lightweight flywheel, and ECS dogbone bushings. So i've pretty much got everything from the reliable/inexpensive mods thread covered.

The problem is, I'm getting sick of catching people in the corners at the track, and not getting to pass them because they walk away on the straights!

Cheap? A bigger cam. A 276* with HD valve springs would give you a bunch more HP, and a SRI would give you more top end, too. You'd probably gain like 15-20bhp there over the 260 cam and the stock ported mk4 manifold.

Ideally? A bigger cam (268/260 or a 276* 114*lc) with HD springs and a turbo kit from C2 or a BBM kit.. Or a Neuspeed kit. Lots of gains with FI on these little 8v's.

Wife has a Neuspeed S/C on her MK4 with a 268/260, 2.5" exhaust, and a few other mods and it's a nice smooth car to drive even with the automatic. It's probably around 145whp or so. Not fast, but not slow. Beats my friend's stock 1.8T 5 speed.

Without doing serious headwork and/or forced induction, there's not a whole lot you can expect. If you really want to go faster, it's time to spend bigger bucks. A bigger cam will give you a bit more power, but don't expect a phenomenal gain.

I've got a 276* cam with dual springs and matched software, AEG intake, open MAF with no air filter at the moment (yeah I know, I know), Raceland header, TT catback. It's definitely a good deal faster than stock, but I still get smoked in the straights by just about every newer stock car on the road. This is a MKIII GTI, your MKIV is a good bit heavier than that too.

Last edited by Anony00GT; 09-29-2012 at 03:08 PM.

2012 Corolla
1998 GTI 2.0T

World Automotive
Need any VCDS (VAG-COM) diagnostics or coding in the North NJ area? PM me.

Without doing serious headwork and/or forced induction, there's not a whole lot you can expect. If you really want to go faster, it's time to spend bigger bucks.

I understand that it's time to spend a fair bit more money, that's the intent of this thread. I won't be doing this stuff right away, but I want to have a plan for what I'm saving money for. I think I've pretty much got the bolt-ons covered (other than SRI), so now it's time for me to learn the serious work.

What sort of things can be done as far as headwork, and what might I be able to do myself? For the near future I'm considering picking up another head that I can work on and eventually swap in. What sort of gains would oversize valves give (such as TT has on their site)? I assume this would require matching seats to be machined on the head. Would I get the head to breathe much better if I ported the manifold side, or is there not much room to be had there?

Plans for the more distant future (when I retire this car to track only use) will be a 20/20 conversion (turbo'd of course).

If anyone has links to some really good build threads, I'd love to see them.

Also quick question - do you take out your rear seats or spare tire when taking it on the track to try and improve the power to weight?

Yes I do remove my rear seats. The seat backs have quite a bit of weight to them, so it definitely improves acceleration. It's debatable what it does to handling as it makes the car even more front-balanced, but I personally think that I feel more rotation with them out (at least on turn in and throttle off conditions) as it un-weights the rear without adding extra weight to the front.

Care to detail each of these? I haven't really started into the world of 'serious' engine building yet, so while I've heard the terms, I don't necessarily know what they mean, lol.

Decking would be planing the bottom face of the head to make sure it's flat, but mostly to increase compression?
Porting meaning the manifold side of the head?

I've heard of people doing muilti-angle valve seats or whatever, but how do you decide on the angles?
For polishing, what exactly gets polished? TT has 2 different plus sizes for valves available IIRC, what difference would each make? If it's just 'bigger is better' then why are there 2 plus sizes?

I'm sure these seem like very noob questions, but the answers need to be found somewhere. I'm off to google next

Larger Valves

So far from google I've found that larger intake valves will improve top end power while sacrificing low end torque. Because there is less restriction, the air will enter the head at a lower speed. At low rpms this means that there will be less diffusion inside the combustion chamber, causing less air to be pulled in. At higher rpms however, the vacuum and relative speeds generated will allow more air to flow into the head (relative to smaller valves). I've not found any information on larger exhaust valves, however I have learned that the valve itself may be less critical in the system for the exhaust side (due to the vacuum being generated outside the combustion chamber).

Port and Polish

Again, from some prior knowledge, and google:
A beginners (stage 1 I suppose?) port and polish would consist of smoothing off any molding defects/flash, and gasket matching the intake and exhaust ports.

The intake port should remain somewhat rough so as to aid in the atomization of any fuel vapours that should condense on the walls. The combustion chamber and exhaust ports can be polished to a greater degree, but by no means is it necessary to achieve a mirror finish.

Valve seat modification should only be attempted by professionals to ensure that the valves can still maintain compression

Please advise me if I am incorrect in any way, I am still a beginner just learning from research. Hopefully more in depth discussion and descriptions of more advanced changes to be made can follow.

Decked

More google research:
Decking refers to machining off a small amount of material from the base of the head. This ensures a smooth and flat surface for sealing and mounting your head, but it also increases the compression ratio.

Potential issues to be addressed when decking your head (found in forums for other motors, unsure if the same issues rise when decking these heads)
1- since you head is now mounted 'lower' your valves will be moving closer to your pistons. It does not sound like there are any cams out there for our motors with a high enough lift for this to matter.
2- mounting your head 'lower' will also change your timing to some degree. If you are going this in depth with your engine, you will probably have an adjustable cam gear, so you just need to dial it in on the dyno. (likely only a degree or 2 off)
3- Higher CR means higher grade gas to avoid knocking. By this I mean just going with 91 octane, no need for racing fuel or anything

1- since you head is now mounted 'lower' your valves will be moving closer to your pistons. This only becomes a concern if you are running a very high lift cam (are there any cams out there for this motor that it could be a concern for?
2- mounting your head 'lower' will also change your timing to some degree. If you are going this in depth with your engine, you will probably have an adjustable cam gear, so you just need to dial it in on the dyno. (likely only a degree or 2 off)
3- Higher CR means higher grade gas to avoid knocking

Did I miss anything?

1. You shouldn't run into any issues at all.

2. The only problem would be the timing, and that is easily fixed with an adjustable cam gear.

3. Don't worry about the compression. Just use 91+ octane and you'll be fine.

Does anyone have good tips for multi-angle valve seats? There should be plenty of guys out there with this done already, but I haven't seen anyone actually list their angles, or any details other than a simple, "It's got a 3 angle valve job," though it seems like the better builds have 5 angles...